Sudden branch death on Knockouts
One of my Knockouts has multiple branches suddenly dying. The leaves turn brown without falling off, and display no obvious pathology. I cut several of the branches today and saw nothing abnormal in the wood. My first thought was rot rot, but shouldn't the whole plant die in that case? Several other branches display distress - leaves look dehydrated and are losing color. The death is so sudden that some of the branches still have old blooms on them, so very recently they were healthy enough to bloom.